Variable displacement compressor

ABSTRACT

A variable displacement compressor has a housing, a piston, a drive shaft, a rotor, a cam plate and a hinge mechanism. The hinge mechanism between the rotor and the cam plate guides the cam plate to incline and slide relative to the drive shaft. Thus, the displacement volume of the compressor is varied. The rotation of the drive shaft is converted to the reciprocation of the piston through the rotor, the hinge mechanism and the cam plate. The hinge mechanism includes first and second hinge elements that are respectively provided on the rotor and on the cam plate and engage each other. At least one of the first and second hinge elements has a degree of freedom for motion against the rotor and/or the cam plate to which it belongs.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a variable displacement pistontype compressor for use in a vehicle air conditioner.

[0002] Unexamined Japanese Patent Publication No. 9-203377 discloses avariable displacement compressor of such type. FIG. 14 illustrates apartially longitudinal cross-sectional view of a variable displacementcompressor according to a prior art. A housing 101 of the compressordefines a cylinder bore 101 a that accommodates a piston 102. A driveshaft 103 is rotatably supported by the housing 101. A rotor 104 isconnected to the drive shaft 103 so as to rotate integrally therewith. Aswash plate 105 is supported by the drive shaft 103 so that it slidesand inclines relative to the drive shaft 103. The piston 102 engages theperiphery of the swash plate 105 through a pair of shoes 107. A hingemechanism 108 is interposed between the rotor 104 and the swash plate105.

[0003] Accordingly, the rotation of the drive shaft 103 is converted tothe reciprocation of the piston 102 through the rotor 104, the hingemechanism 108 and the swash plate 105, while the swash plate 105 isguided by the hinge mechanism 108 to slide on the drive shaft 103 inaccordance with the inclination of the swash plate 105. Thus, thedisplacement volume of the compressor is varied.

[0004] The hinge mechanism 108 includes a pair of first protrusions 108a (only one is shown in FIG. 14), a second protrusion 108 b and a camsurface 108 c. The first protrusions 108 a extend from the rotor 104toward the swash plate 105. The second protrusion 108 b extends from theswash plate 105 toward the rotor 104. The distal end of the secondprotrusion 108 b is inserted between the first protrusions 108 a. Thecam surface 108 c is formed at the proximal portion of the firstprotrusions 108 a. The first protrusions 108 a and the second protrusion108 b contact with a certain amount of area to engage each other so thatthe rotation of the rotor 104 is transmitted to the swash plate 105through the hinge mechanism 108. The distal end of the second protrusion108 b slidably contacts the cam surface 108 c so that axial load thatacts on the swash plate 105 due to compression reactive force isreceived by the cam surface 108 c through the second protrusion 108 b.

[0005] In the hinge mechanism 108, the first protrusions 108 a and thesecond protrusion 108 b are integrally formed with the rotor 104 and theswash plate 105, respectively. An unwanted feature is that as the swashplate 105 inclines to twist the second protrusion 108 b by the pair offirst protrusions 108 b due to offset axial load based upon thecompression reactive force, sliding resistances increase between theside surfaces of the first protrusions 108 a and the second protrusion108 b and between the distal end of the second protrusion 108 b and thecam surface 108 c due to the contact of the edge. This leads to earlyabrasion of each sliding surface. In other words, durability of thehinge mechanism 108 is deteriorated, and unsmooth operation of the hingemechanism 108 leads to deteriorated controllability for the displacementvolume of the compressor. Therefore, there is a need for a variabledisplacement compressor that improves durability of a hinge mechanismand that ensures smooth operation of the hinge mechanism.

SUMMARY OF THE INVENTION

[0006] In accordance with the present invention, a variable displacementcompressor has a housing, a piston, a drive shaft, a rotor, a cam plateand a hinge mechanism. The housing defines a cylinder bore. The pistonis accommodated in the cylinder bore. The drive shaft is rotatablysupported by the housing. The rotor is connected to the drive shaft soas to rotate integrally with. The cam plate is supported by the driveshaft so as to slide and incline relative to the drive shaft and isoperatively connected to the piston. The hinge mechanism is interposedbetween the rotor and the cam plate and guides the cam plate to inclineand slide relative to the drive shaft. Thus, the displacement volume ofthe compressor is varied. The rotation of the drive shaft is convertedto the reciprocation of the piston through the rotor, the hingemechanism and the cam plate. The hinge mechanism includes a first hingeelement and a second hinge element. The first hinge element is providedon the rotor. The second hinge element is provided on the cam plate andis engaged with the first hinge element. At least one of the first andsecond hinge elements has a degree of freedom for motion against therotor and/or the cam plate to which the hinge element having the degreeof freedom for motion belongs.

[0007] Other aspects and advantages of the invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The features of the present invention that are believed to benovel are set forth with particularity in the appended claims. Theinvention together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

[0009]FIG. 1 is a longitudinal cross-sectional view of a variabledisplacement compressor according to a first preferred embodiment of thepresent invention;

[0010]FIG. 2 is a side view of a hinge mechanism according to the firstpreferred embodiment of the present invention;

[0011]FIG. 3 is a plan view of the hinge mechanism according to thefirst preferred embodiment of the present invention;

[0012]FIG. 4 is a hinge element of a swash plate according to the firstpreferred embodiment of the present invention;

[0013]FIG. 5 is an enlarged longitudinal cross-sectional view of a hingemechanism according to a second preferred embodiment of the presentinvention;

[0014]FIG. 6 is a plan view of a hinge mechanism according to a thirdpreferred embodiment of the present invention;

[0015]FIG. 7 is an enlarged side view of a hinge mechanism according toa fourth preferred embodiment of the present invention;

[0016]FIG. 8 is an enlarged longitudinal cross-sectional view of a hingemechanism according to a fifth preferred embodiment of the presentinvention;

[0017]FIG. 9 is a plan view of a hinge mechanism according to a sixthpreferred embodiment of the present invention;

[0018]FIG. 10 is an enlarged longitudinal cross-sectional view of ahinge mechanism according to a seventh preferred embodiment of thepresent invention;

[0019]FIG. 11 is an enlarged perspective view of the hinge mechanismaccording to the seventh preferred embodiment of the present invention;

[0020]FIG. 12 is a longitudinal cross-sectional view of a hingemechanism according to an eighth preferred embodiment of the presentinvention;

[0021]FIG. 13 is a plan view of the hinge mechanism according to theeighth preferred embodiment of the present invention; and

[0022]FIG. 14 is a partially longitudinal cross-sectional view of avariable displacement compressor according to a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A first preferred embodiment of the present invention will now bedescribed with reference to FIGS. 1 through 4. The present invention isapplied to a variable displacement compressor for a refrigerant circuitof a vehicle air conditioner in the first preferred embodiment. The leftside and the right side respectively correspond to the front side andthe rear side of the compressor in FIG. 1.

[0024]FIG. 1 illustrates a longitudinal cross-sectional view of thevariable displacement compressor according to the first preferredembodiment of the present invention. A housing of the compressorincludes a cylinder block 11, a front housing 12 and a rear housing 14.The front housing 12 is fixedly connected to the front end of thecylinder block 11. The rear housing 14 is fixedly connected to the rearend of the cylinder block 11 through a valve plate assembly 13.

[0025] A crank chamber 15 is defined between the cylinder block 11 andthe front housing 12. A drive shaft 16 is rotatably supported by thehousing and extends through the crank chamber 15 from the front housing12 to the cylinder block 11. The drive shaft 16 is rotated by the powertransmitted from an engine (not shown) for traveling a vehicle.

[0026] In the crank chamber 15, a rotor 17 made of cast iron is fixedlyconnected to the drive shaft 16 so as to rotate integrally therewith.The front end surface of the rotor 17 and the facing inner wall surfaceof the front housing 12 interpose a thrust bearing 35. The crank chamber15 accommodates a swash plate or a cam plate 18. The swash plate 18 ismade of iron series metal, such as iron and iron alloy. The swash plate18 is formed by forging.

[0027] A through hole 20 is formed at the center of the swash plate 18.The drive shaft 16 extends through the through hole 20. The swash plate18 is supported by the drive shaft 16 through an inner surface 20 a ofthe through hole 20 in such a manner that the swash plate 18 inclinesand slides relative to the drive shaft 16. A circular clip 32 is fittedon the drive shaft 16 on the rear side to the swash plate 18. A coilspring 33 for increasing inclination angle of the swash plate 18 isarranged between the circular clip 32 and the swash plate 18 so as tourge the middle portion of the swash plate 18 forward.

[0028] A hinge mechanism 19 is interposed between the rotor 17 and theswash plate 18. The hinge mechanism 19 includes a first hinge element 52provided on the rotor 17 and a second hinge element 51 provided on theswash plate 18. The swash plate 18 is coupled to the rotor 17 throughthe hinge mechanism 19 and is supported by the drive shaft 16 throughthe inner surface 20 a of the though hole 20. Accordingly, the swashplate 18 is integrally rotatable with the rotor 17 and the drive shaft16, while it is inclinable relative to the drive shaft 16 in accordancewith sliding movement in the direction of the axis L of the drive shaft16.

[0029] Incidentally, with respect to the swash plate 18, the innersurface 20 a of the through hole 20 is treated by induction hardeningfor improving sliding performance against the drive shaft 16 and forimproving abrasion resistance.

[0030] A plurality of cylinder bores 22 (one of them shown in FIG. 1)extends through the cylinder block 11 and is arranged around the axis Lof the drive shaft 16 at equiangular positions. Each of the cylinderbores 22 accommodates a single-headed piston 23 so as to be reciprocatedtherein. The front and rear openings of each cylinder bore 22 arerespectively closed by the top end surface of the piston 23 and thefront end surface of the valve port assembly 13. Thus, a compressionchamber 24 is defined in each of the cylinder bores 22 and varies itsvolume in accordance with the reciprocation of the respective piston 23.Each of the pistons 23 engages the outer periphery of the swash plate 18through a pair of semispherical shoes 25. Accordingly, the rotation ofthe swash plate 18 in accordance with the rotation of the drive shaft 16is converted to the reciprocation of the piston 23 through the shoes 25.

[0031] Incidentally, with respect to the swash plate 18, slidingsurfaces 18b against the respective shoes 25 are treated by inductionhardening for improving sliding performance against the shoes 25 and forimproving abrasion resistance.

[0032] A suction chamber 26 and a discharge chamber 27 are definedbetween the valve plate assembly 13 and the rear housing 14. Therefrigerant gas in the suction chamber 26 is introduced into thecompression chamber 24 through a suction port 28 and a suction valve 29as each piston 23 moves from its top dead center to its bottom deadcenter. The suction port 28 and the suction valve 29 are formed in thevalve plate assembly 13. The refrigerant gas in the compression chamber24 is compressed to a predetermined pressure value as the piston 23moves from the bottom dead center to the top dead center. The compressedrefrigerant gas is discharged to the discharge chamber 27 through adischarge port 30 and a discharge valve 31, which are formed in thevalve plate assembly 13.

[0033] The compressor optionally varies its displacement volume andregulates its displacement volume in such a manner that a control valve21 adjusts pressure in the crank chamber 15. In other words, pressuredifferential between the crank chamber 15 and the compression chambers24 is varied by the control valve 21 in response to variation of thepressure in the crank chamber 15. As a result, the inclination angle ofthe swash plate 18 is varied, and the stroke of the piston 23 isadjusted.

[0034] As the pressure in the crank chamber 15 decreases, the swashplate 18 is pushed by the coil spring 33 to increase its inclinationangle. Thus, the strokes of the pistons 23 increase, and thedisplacement volume of the compressor increases. The front end surfaceof the swash plate 18 has a portion 18 a for regulating maximuminclination angle. The portion 18 a also serves as a balance weight. Themaximum inclination angle of the swash plate 18 is regulated in such amanner that the portion 18 a contacts the rear end surface of the rotor17, as shown in FIG. 1.

[0035] On the other hand, as the pressure in the crank chamber 15increases, the swash plate 18 resists against the coil spring 33 todecrease its inclination angle. Thus, the strokes of the pistons 23decrease, and the displacement volume of the compressor decreases. Theminimum inclination angle of the swash plate 18 is regulated by thecircular clip 32 and the coil spring 33.

[0036]FIG. 2 illustrates a side view of the hinge mechanism 19 accordingto the first preferred embodiment of the present invention. FIG. 3illustrates a plan view of the hinge mechanism 19 according to the firstpreferred embodiment of the present invention. Now referring to FIGS. 1through 3, an engaging recess 41 is formed at the rear end of the rotor17 and faces a point TDC of the swash plate 18. The point TDC is acenter of the hypothetical spherical surface of the shoes 25 when thepiston 23 is positioned at a top dead center. The engaging recess 41 isdefined by a pair of first protrusions 43 that extend toward the swashplate 18. The first protrusions 43 are respectively disposed at the rearend on a preceding side and on a following side in the rotationaldirection of the rotor 17.

[0037] A pair of second protrusions 44 extends toward the rotor 17 andis arranged at the front end of the swash plate 18 so as to face theengaging recess 41. The second protrusions 44 are respectively disposedon a preceding side and on a following side in the rotational directionof the drive shaft 16 so as to interpose a hypothetical plane includingthe axis L and the point TDC. Each of the distal ends of the secondprotrusions 44 fits into the engaging recess 41. Each of the secondprotrusions 44 includes a side surface 44 a that faces away from eachother. Each of the side surfaces 44 a contacts a side surface 43 a ofthe first protrusion 43 with a certain amount of area. The side surfaces43 a partially form the inner surface of the engaging recess 41.Accordingly, the rotational power of the rotor 17 is transmitted to theswash plate 18 through one of the first protrusions 43 (the sidesurfaces 43 a) and one of the second protrusions 44 (the side surfaces44 a).

[0038] Incidentally, to improve general-purpose property, with respectto the compressor of the first preferred embodiment, the hinge mechanism19 is symmetrically formed relative to the the hypothetical planeincluding TDC and the axis L along the rotational direction of the driveshaft 16 so as to appropriately respond either rotational direction ofthe drive shaft 16, even if a mounted engine rotates in eitherdirection.

[0039] A cam portion 45 for receiving axial load is formed on theproximal portion of each first protrusion 43 in the engaging recess 41.The cam portions 45 and the first protrusions 43 constitute the firsthinge element 52 on the side of the rotor 17. The rear end surface ofeach cam portion 45 facing the swash plate 18 forms a cam surface 45 athat protrudes toward the rear side as it approaches the drive shaft 16.Each of the second protrusions 44 forms a convex circular arc surface 44b and slidably contacts the cam surface 45 a of the corresponding camportion 45 by the circular arc surface 44 b. Accordingly, the axial loadthat acts on the swash plate 18 due to the compression reactive force isreceived by the cam surfaces 45 a of the cam portions 45 through thecircular arc surfaces 44 b of the second protrusions 44, respectively.

[0040] With respect to the prior art shown in FIG. 14, the hingemechanism 108 includes the single and relatively large-scaled secondprotrusion 108 b. However, in the first preferred embodiment, the secondprotrusion 108 b of the prior art is divided into the two secondprotrusions 44. The above structure ensures the same width for receivingaxial load as that of the second protrusion 108 b of the prior art andlightens the swash plate assembly 18, 51 by changing the structure ofthe second protrusion 108 b of the prior art to a hollow structure.

[0041] As the compressor increases its displacement volume, the distalends of the second protrusions 44 rotate around a central axis S of thecircular arc surfaces 44 b in the clockwise direction in FIG. 1, whilethey move on the cam surfaces 45 a of the respective cam portions 45away from the drive shaft 16. Thus, the hinge mechanism 19 guides toincrease the inclination angle of the swash plate 18. On the contrary,when the compressor reduces its displacement volume, the distal ends ofthe second protrusions 44 rotate around the central axis S of thecircular arc surfaces 44 b in the counterclockwise direction in FIG. 1,while they move on the cam surfaces 45 a of the cam portions 45 toapproach the drive shaft 16. Thus, the hinge mechanism 19 guides toreduce the inclination angle of the swash plate 18.

[0042] Incidentally, the first hinge element 52 and the second hingeelement 51 slide on each other at sliding surfaces, such as the sidesurfaces 43 a, 44 a of the respective first and second protrusions 43,44, the circular arc surfaces 44 b of the respective second protrusions44, and the cam surfaces 45 a of the respective cam portions 45. Theabove sliding surfaces are treated by induction hardening for improvingtheir sliding performance and abrasion resistance.

[0043] In the second hinge element 51, the induction hardening mayexclusively be treated at a portion including the side surfaces 44 a andthe circular arc surfaces 44 b or may entirely be treated. Particularly,the former treatment restrains the distortion and crack of the secondhinge element 51 of the swash plate 18 due to heat affection of thehardening. Incidentally, the induction hardening may be treated only atportions including the side surfaces 43 a and the cam surfaces 45 a ormay be treated at the entire first hinge element 52. Particularly, theformer treatment restrains the distortion and crack of the first hingeelement 52 due to heat affection of the hardening.

[0044] As shown in FIGS. 1 through 3, the second hinge element 51 isseparately formed from the swash plate 18. The second hinge element 51includes a base plate or a base 47 and a pair of second protrusions 44that extend from the front end surface of the base plate 47. The swashplate 18 is made of iron series metal and is formed by forging. On theother hand, the second hinge element 51 is made of aluminum seriesmetal, such as aluminum and aluminum alloy. That is, the second hingeelement 51 is made of different material from that of the swash plate18, and the second protrusions 44 and the base plate 47 are integrallyformed by forging or by molding. With respect to the swash plate 18, thesliding surfaces 18 b against the shoes 25 and the inner surface 20 a ofthe through hole 20 are polished and treated by induction hardeningbefore the second hinge element 51 is assembled to the swash plate 18.

[0045] In the second hinge element 51, a shaft 48 is integrally formedat the center of the rear end surface of the base plate 47 and extendsvertically relative to the base plate 47. In the swash plate 18, a shafthole 18 c is recessed inwardly from the sliding surfaces 18 b againstthe shoes 25 and extends in thickness of the swash plate 18. The secondhinge element 51 is loosely fitted into the shaft hole 18 c of the swashplate 18 by the shaft 48.

[0046] Accordingly, referring to FIG. 4, the diagram illustrates thesecond hinge element 51 according to the first preferred embodiment ofthe present invention. The second hinge element 51 is rotatable on theswash plate 18 relative to an axis M of the shaft 48 (or the shaft hole18 c). Namely, the second hinge element 51 has the degree of freedom forrotation against the swash plate 18 to which the second hinge element 51belongs. The rotation of the second hinge element 51 is regulated in apredetermined angular range in such a manner that an end surface 47 a ofthe base plate 47 near the drive shaft 16 contacts the wall surface of astep or a regulating means 18 d formed on the front end surface of theswash plate 18.

[0047] Incidentally, referring back to FIGS. 1 and 2, a lighteningrecess 48 a is formed at the distal end of the shaft 48 on the side nearthe drive shaft 16 so that the swash plate 18 avoids interfering withthe coil spring 33 when positioned at the maximum inclination angle.

[0048] The following advantageous effects are obtained from the firstpreferred embodiment.

[0049] (1) The second hinge element 51 has the degree of freedom formotion against the swash plate 18. Accordingly, even if offset axialload due to the compression reactive force acts on the inclined swashplate 18 to twist the second protrusions 44 in the engaging recess 41,stress due to the inclined swash plate 18 moves the second hinge element51 so that the second protrusions 44 avoid twisting in the engagingrecess 41. As a result, the side surfaces 44 a of the respective secondprotrusions 44 and the side surfaces 43 a of the respective firstprotrusions 43 contact each other with a certain amount of area, whilethe circular arc surfaces 44 b of the respective second protrusions 44and the cam surfaces 45 a of the respective cam portions 45 contact eachother with a line. Thus, no edge abuts at each sliding surface.Accordingly, the hinge mechanism 19 smoothly moves, and the displacementvolume of the compressor smoothly varies.

[0050] (2) The second hinge element 51 on the swash plate 18 has thedegree of freedom for rotation. In comparison to a hinge mechanism thathas a degree of freedom for sliding, the second hinge element 51effectively avoids the second protrusions 44 from twisting in theengaging recess 41.

[0051] (3) The rotation of the second hinge element 51 is regulated in apredetermined angular range in such a manner that the second hingeelement 51 contacts the step 18 d formed on the swash plate 18.Accordingly, the second hinge element 51 is prevented from excessivelyrotating on the swash plate 18 so that noise due to collision betweenthe second protrusions 44 and the first protrusions 43 is reduced. Thestructure for regulating the rotation of the second hinge element 51helps to assemble the swash plate assembly 18, 51 to the compressor,that is, the structure helps to easily insert the second protrusions 44into the engaging recess 41. Namely, for example, without the structurefor regulating the rotation of the second hinge element 51, the rotationof the second hinge element 51 must be temporarily regulated to fit thesecond protrusions 44 into the engaging recess 41. Accordingly, a jigfor regulating the rotation of the second hinge element 51 is requiredso that assembling becomes complicated.

[0052] (4) Since the second hinge element 51 has the degree of freedomfor motion against the swash plate 18, that is, since the second hingeelement 51 is separately formed from the swash plate 18, the shape ofthe swash plate 18 becomes simple. Accordingly, the swash plate 18employs forging as a manufacturing procedure because forging providesbetter yield and easy after-machining in comparison to molding. Even ifthe second hinge element 51 needs to be separately formed and assembledto the swash plate 18, costs are reduced for manufacturing thecompressor. Incidentally, the swash plate 18 formed by forging hasrelatively high hardenability in comparison to the one formed bymolding.

[0053] The separately formed swash plate 18 and the second hinge element51 permit appropriate selection for their respective material.Accordingly, in the first preferred embodiment, the swash plate 18 ismade of iron series metal that has relatively high relative density forensuring its strength and for ensuring moment for stable variation ofthe displacement volume. Additionally, the second hinge element 51 thatis arranged at an offset position on the swash plate 18 is made ofaluminum series metal that has relatively low relative density forbalancing around the axis L of the swash plate assembly 18, 51. Thesecond hinge element 51 made of light aluminum series metal helps thebalance weight 18 a for balancing around the axis L of the second hingeelement 51 to be compact. This leads to the lightened swash plateassembly 18, 51 and to the lightened compressor.

[0054] Furthermore, the second hinge element 51 made of aluminum seriesmetal that is different from that of the first hinge element 52 made ofcast iron effectively prevents a same-metal phenomenon due to slidebetween the first hinge elements 52. The same-metal phenomenon meansthat mutually same metals lead to inconveniences such as an increase incoefficient of friction.

[0055] (5) In the first and second hinge elements 51, 52 for the hingemechanism 19, the second hinge element 51 is separately formed from theswash plate 18. Accordingly, a depth for fitting the shaft 48 into theshaft hole 18 c may be relatively long in the direction of the axis M sothat the swash plate 18 supports the second hinge element 51 in stable.As a result, for example, the second hinge element 51 may be rotated instable relative to the swash plate 18 so as to avoid twisting of thesecond protrusions 44 in the engaging recess 41. This leads to smoothoperation of the hinge mechanism 19 and to smooth variation of thedisplacement volume of the compressor.

[0056] Namely, for example, according to a second preferred embodimentof FIG. 5 which will be described later, when the first hinge element 52is separately formed from the rotor 17, the distal end of the shaft 55needs consideration for not protruding the distal end of the shaft 55from the shaft hole 17 a including dimensional tolerance so as to avoidinterference between the shaft 55 and the thrust bearing 35 (See FIG. 1)that is arranged on the front end surface of the rotor 17. Accordingly,the depth for fitting between the shaft 55 and the shaft hole 17 a tendsto become small in the direction of the axis M so that the rotor 17supports the first hinge element 52 in unstable.

[0057] (6) When the swash plate 18 is separately formed from the secondhinge element 51, the second hinge element 51 does not interfere withthe approach of a grind stone to the sliding surface 18 b in a polishingprocess of the sliding surfaces 18 b that slide on the shoes 25 beforethe second hinge element 51 is assembled to the swash plate 18.Therefore, workability of the swash plate 18 becomes better. In otherwords, the second hinge element 51 does not need to consider theinterference when the sliding surfaces 18 b are polished and permitsfree determination of its shape and also permits ideal shape fortransmitting power and for guiding inclination of the swash plate 18.

[0058] (7) The second hinge element 51 includes a pair of the secondprotrusions 44 that are integrated with each other and is rotatable onthe swash plate 18. In comparison to a plurality of the secondprotrusions 44 that are individually rotatable on the swash plate 18,the structure of the second hinge element 51 for rotation, that Is, thestructure for increasing the degree of freedom, may be simple in thefirst preferred embodiment. Additionally, a plurality of the integratedsecond protrusions 44 leads to easy setting in high accuracy the widthbetween the side surfaces 44 a of the respective second protrusions 44.The width largely affects the smooth operation of the hinge mechanism19.

[0059] (8) The swash plate 18 that is separately formed from the secondhinge element 51 is treated by hardening at sliding surfaces 18 bagainst the shoes 25 and the inner surface 20 a of the through hole 20that slides on the drive shaft 16 before the second hinge element 51 isassembled to the swash plate 18. Accordingly, the second hinge element51 does not receive heat affection due to hardening and avoidsdistortion due to the heat affection. No modification for distortion ofthe second hinge element 51 is required, but the hinge mechanism 19smoothly operates so that costs are reduced for manufacturing thecompressor.

[0060] A second preferred embodiment of the present invention will nowbe described with reference to FIG. 5. The components that are differentfrom those of the first preferred embodiment are only described. Thesame reference numerals denote the substantially identical components tothose of the first preferred embodiment, and the description is omitted.

[0061]FIG. 5 illustrates an enlarged longitudinal cross-sectional viewof the hinge mechanism 19 according to the second preferred embodimentof the present invention. In the second preferred embodiment, the secondhinge element 51 is integrally formed with the swash plate 18, while thefirst hinge element 52 is separately formed from the rotor 17. The firsthinge element 52 integrally forms a base plate 56, a pair of the firstprotrusions 43 and a pair of the cam portions 45. The first protrusions43 extend from the rear end surface of the base plate 56. The camportions 45 are formed on the proximal portions of the respective firstprotrusions 43. The rotor 17 that is separately formed from the firsthinge element 52 is simple and may apply forging as a manufacturingprocedure.

[0062] The first hinge element 52 is loosely fitted into a shaft hole 17a at a shaft 55 thereof. The shaft 55 extends from the front end surfaceof the base plate 56. The shaft hole 17 a is formed through the rotor17. Accordingly, the first hinge element 52 is rotatable on the rotor 17around the axis M of the shaft 55 (or the shaft hole 17 a) that isparallel with the axis L of the drive shaft 16. Namely, the first hingeelement 52 has the degree of freedom for rotation against the rotor 17.The rotation of the first hinge element 52 is regulated in apredetermined angular range on the rotor 17 in such a manner that an endsurface 56 a facing the drive shaft 16 contacts the wall surface of thestep 17 b that is formed on the rotor 17.

[0063] In the second preferred embodiment, the first hinge element 52 isrotatable on the rotor 17. Accordingly, even if the swash plate 18inclines to twist the second protrusions 44 in the engaging recess 41 bythe axial load due to the compression reactive force, stress due to theinclination rotates the first hinge element 52 around the axis M on therotor 17 so as to prevent the swash plate 18 from twisting the secondprotrusions 44.

[0064] A third preferred embodiment of the present invention will now bedescribed with reference to FIG. 6. The components that are differentfrom those of the first preferred embodiment are only described. Thesame reference numerals denote the substantially identical components tothose of the first preferred embodiment, and the description is omitted.

[0065]FIG. 6 illustrates a plan view of the hinge mechanism 19 accordingto the third preferred embodiment of the present invention. In the thirdpreferred embodiment, the engaging recess 41 is formed between a pair ofthe second protrusions 44 in the second hinge element 51. The rotor 17includes the single first protrusion 43 at its rear end surface facingthe engaging recess 41. The first protrusion 43 extends toward the swashplate 18. The distal end of the first protrusion 43 is inserted in theengaging recess 41. The first protrusion 43 has a pair of side surfaces43 b, while each of the second protrusions 44 has a side surface 44 cthat is a part of the inner surface of the engaging recess 41. The sidesurfaces 43 b of the first protrusion 43 contact the side surfaces 44 cwith a certain amount of area. Accordingly, the rotational power of therotor 17 is transmitted to the swash plate 18 through one of the sidesurfaces 43 b of the first protrusion 43 and one of the side surfaces 44c of the respective second protrusions 44.

[0066] The second hinge element 51 includes the cam portion 45 at theproximal portions of the second protrusions 44 in the engaging recess41. The distal end of the first protrusion 43 forms a convex circulararc surface 43 d and slidably contacts a cam surface 45 c of the camportion 45. Accordingly, the axial load that acts on the swash plate 18due to the compression reactive force is received by the cam surface 45c of the cam portion 45.

[0067] A fourth preferred embodiment of the present invention will nowbe described with reference to FIG. 7. The components that are differentfrom those of the first preferred embodiment are only described. Thesame reference numerals denote the substantially identical components tothose of the first preferred embodiment, and the description is omitted.

[0068]FIG. 7 illustrates an enlarged side view of the hinge mechanism 19according to the fourth preferred embodiment of the present invention.In the fourth preferred embodiment, the side surface 43 a of the firstprotrusion 43 includes a guide groove 43 c that extends along thedirection of the cam surface 45 a of the cam portion 45. The sidesurface 44 a of the second protrusion 44 includes a guide protrusion 44d on the central axis S of the circular arc surface 44 b, and the guideprotrusion 44 d is engagedly inserted in the guide groove 43 c forguiding the swash plate 18 to incline and slide relative to the driveshaft 16.

[0069] Even if the compression reactive force that acts on the swashplate 18 disappears due to the stop of the compressor, or even if thecompression reactive force that acts on the swash plate 18 decreases dueto the operation of the compressor in a minimum displacement volume, theswash plate assembly 18, 51 engages the rotor 17 by the engagementbetween the guide groove 43 c and the guide protrusion 44 d. As aresult, the swash plate assembly 18, 51 is prevented from rattling dueto vibration of a vehicle, with a consequence of preventing noisegenerated on the compressor.

[0070] A fifth preferred embodiment of the present invention will now bedescribed with reference to FIG. 8. The components that are differentfrom those of the first preferred embodiment are only described. Thesame reference numerals denote the substantially identical components tothose of the first preferred embodiment, and the description is omitted.

[0071]FIG. 8 illustrates an enlarged longitudinal cross-sectional viewof the hinge mechanism 19 according to the fifth preferred embodiment ofthe present invention. In the fifth preferred embodiment, a slider 57 isinterposed between the circular arc surface 44 b of the secondprotrusion 44 and the cam surface 45 a of the cam portion 45. Namely,the second protrusion 44 (the circular arc surface 44 b) and the camportion 45 (the cam surface 45 a) slidably contact each other throughthe slider 57.

[0072] The slider 57 includes a concave circular arc surface 57 a and aplanar surface 57 b. The concave circular arc surface 57 a slides on thecircular arc surface 44 b of the second protrusion 44. The planarsurface 57 b slides on the cam surface 45 a. Accordingly, the camportion 45 and the slider 57 contact each other with a certain amount ofarea, and the second protrusion 44 and the slider 57 contact each otherwith a certain amount of area. The areal contacts reduce abrasion of thecam surface 45 a and the circular arc surface 44 b. That is, the arealcontacts contribute to improved durability of the hinge mechanism 19.

[0073] A sixth preferred embodiment of the present invention will now bedescribed with reference to FIG. 9. The components that are differentfrom those of the first preferred embodiment are only described. Thesame reference numerals denote the substantially identical components tothose of the first preferred embodiment, and the description is omitted.

[0074]FIG. 9 illustrates a plan view of the hinge mechanism 19 accordingto the sixth preferred embodiment of the present invention. In the sixthpreferred embodiment, the drive shaft 16 rotates in the direction of anarrow R, and the hinge mechanism 19 is particularly configured toappropriately handle a state when the drive shaft 16 rotates in thedirection of the arrow R.

[0075] Namely, with respect to the hinge mechanism 19, a cam portion 45Aand a second protrusion 44A shown in the lower side of FIG. 9 in acompression cycle mainly receive the axial load that acts on the swashplate 18 based upon the compression reactive force, while the firstprotrusion 43 and another second protrusion 44B shown in the upper sideof FIG. 9 in a suction cycle transmit power from the rotor 17 to theswash plate 18. Then, with respect to the second protrusions 44A, 44B,when absolute amount of load, variation of the load and its variationrate are considered, the second protrusion 44A for receiving the axialload is hard in strength than the second protrusion 44B for powertransmission.

[0076] Then, in the sixth preferred embodiment, the cam surface 45 a ofthe cam portion 45A for receiving the axial load is widened than the camsurface 45 a of the cam portion 45B for power transmission, while thesecond protrusion 44A for receiving the axial load is thicker than thesecond protrusion 44B for power transmission. Thus, the width of thecircular arc surface 44 b of the second protrusion 44A is predeterminedto be wide. Accordingly, the strength of the second protrusion 44A forreceiving the axial load is improved. In comparison to the thickenedsecond protrusions 44A, 44B, an increase in weight is relatively small,while durability of the hinge mechanism 19 is ensured at equivalentlevel in the sixth preferred embodiment.

[0077] A seventh preferred embodiment of the present invention will nowbe described with reference to FIGS. 10 and 11. The components that aredifferent from those of the first preferred embodiment are onlydescribed. The same reference numerals denote the substantiallyidentical components to those of the first preferred embodiment, and thedescription is omitted.

[0078]FIG. 10 illustrates an enlarged longitudinal cross-sectional viewof the hinge mechanism 19 according to the seventh preferred embodimentof the present invention. FIG. 11 illustrates an enlarged perspectiveview of the hinge mechanism 19 according to the seventh preferredembodiment of the present invention. In the seventh preferredembodiment, a slider 60 is supported by the drive shaft 16 so as toslide in the direction of the axis L. A fulcrum shaft 60 a is formedwith the slider 60 and inclinably supports the swash plate 18.

[0079] With respect to the hinge mechanism 19, the cam portion 45 isomitted from the first hinge element 52, and the first and second hingeelements 52, 51 engage each other through link arms 61.

[0080] Namely, the second hinge element 51 includes the single secondprotrusion 44. An insertion hole 44 e is formed through the distal endof the second protrusion 44 in the direction perpendicular to the axis Lof the drive shaft 16. The first hinge element 52 includes the singlefirst protrusion 43 that radially extends from the outer periphery ofthe rotor 17. An insertion hole 43 e is formed through the distal end ofthe first protrusion 43 in the direction perpendicular to the axis L ofthe drive shaft 16.

[0081] A pair of the link arms 61 is arranged on each side of the distalends of the first and second protrusions 43, 44 and each of the linkarms 61 has through holes 61 a, 61 b at both ends. One end of each linkarm 61 is pivotally supported through the through hole 61 a by a pin 62that is inserted into the through hole 43 e of the first protrusion 43.The other end of each link arm 61 is pivotally supported through thethrough hole 61 b by another pin 63 that is inserted through the throughhole 44 e of the second protrusion 44. Accordingly, the swash plate 18inclines around the pins 62, 63 in accordance with slide on the driveshaft 16.

[0082] According to the seventh preferred embodiment, the second hingeelement 51 is rotatable on the swash plate 18. Accordingly, even if theswash plate 18 inclines to twist the second protrusion 44 between thelink arms 61 by the axial load due to the compression reactive force,stress due to the inclination rotates the second hinge element 51 aroundthe axis M on the swash plate 18 so as to prevent the second protrusion44 from twisting between the link arms 61.

[0083] An eighth preferred embodiment of the present invention will nowbe described with reference to FIGS. 12 and 13. The components that aredifferent from those of the first preferred embodiment are onlydescribed. The same reference numerals denote the substantiallyidentical components to those of the first preferred embodiment, and thedescription is omitted.

[0084]FIG. 12 illustrates a longitudinal cross-sectional view of thehinge mechanism 19 according to the eighth preferred embodiment of thepresent invention. FIG. 13 illustrates a plan view of the hingemechanism 19 according to the eighth preferred embodiment of the presentinvention. In the eighth preferred embodiment, the second hinge element51 includes the single second protrusion 44. A through hole 44 f isformed through the distal end of the second protrusion 44. A pin 65 isfixedly inserted into the through hole 44 f in the directionperpendicular to the axis L of the drive shaft 16. With respect to thefirst hinge element 52, a cam groove 43 f is formed in each of the firstprotrusions 43. The second protrusion 44 is inserted in between thefirst protrusions 43 so as to permit power transmission from the rotor17 to the swash plate 18 by contacting the side surfaces 43 a, 44 athrough a washer 67 and to slidably contact the inner surface of the camgroove 43 f by a cylindrical surface 65 a of both sides of the pin 65that is inserted into the cam groove 43 f.

[0085] Accordingly, the axial load that acts on the swash plate 18 dueto the compression reactive force and the like is received by the innersurface of the cam groove 43 f of the first protrusion 43 through thepin 65 of the second hinge element 51. When the swash plate 18 variesits inclination angle, the hinge mechanism 19 guides to increase theinclination angle of the swash plate 18 in such a manner that the pin 65(the cylindrical surface 65 a) moves away from the drive shaft 16 alongthe inner surface of the cam groove 43 f on the side of the rotor 17,while the distal end of the second protrusion 44 rotates around acentral axis of the pin 65.

[0086] According to the eighth preferred embodiment, the second hingeelement 51 is rotatable on the swash plate 18. Accordingly, even if theswash plate 18 inclines to twist the second protrusion 44 between thefirst protrusions 43 and also inclines to twist the pin 65 in the camgroove 43 f by the axial load due to the compression reactive force,stress due to the inclination rotates the second hinge element 51 aroundthe axis M on the swash plate 18 so as to avoid their twisting.

[0087] The present invention is not limited to the embodiments describedabove but may be modified into the following alternative embodiments.

[0088] In alternative embodiments to those of the above first and thirdthrough eighth preferred embodiments, the second hinge element 51 ismade of iron series sintered metal. In alternative embodiments to thoseof the above second preferred embodiment, the first hinge element 52 ismade of iron series sintered metal. Accordingly, the sintered metaleffectively holds lubricating oil so that sliding performance andseizure resistance improve between the first and second hinge elements52, 51. Incidentally, the lubricating oil is supplied to the crankchamber 15 with its mist contained in the refrigerant gas.

[0089] In alternative embodiments to those of the above preferredembodiments, the second hinge element 51 is rotatable on the swash plate18, while the first hinge element 52 is rotatable on the rotor 17.

[0090] In alternative embodiments to those of the above second preferredembodiment, the first protrusion 43 is only rotatable on the rotor 17 inthe components 43, 45 of the first hinge element 52, while the camportion 45 is fixed to the rotor 17. Similarly, in alternativeembodiments to those of the above third preferred embodiment, the secondprotrusion 44 is only rotatable on the swash plate 18 in the components44, 45 of the second hinge element 51, while the cam portion 45 is fixedto the swash plate 18.

[0091] In alternative embodiments to those of the above first and thirdthrough eighth preferred embodiments, a plurality of the secondprotrusions 44 is separately formed, and each of the second protrusions44 is individually rotatable on the swash plate 18.

[0092] In alternative embodiments to those of the above preferredembodiments, a plane bearing or a rolling bearing is interposed betweenthe shaft portion 48 or 55 and the shaft hole 18 c or 17 a,respectively. Also, solid lubricant such as fluororesin and molybdenumdisulfide is applied on at least one of the outer circumferentialsurface of the shaft portion 48 or 55 and the inner circumferentialsurface of the shaft hole 18 c or 17 a, respectively. Accordingly, thesecond hinge element 51 smoothly rotates on the swash plate 18 accordingto the first and third through eighth preferred embodiments or the firsthinge element 52 smoothly rotates on the rotor 17 according to thesecond preferred embodiment. As a result, the swash plate 18 smoothlyvaries its inclination angle. That is, the compressor smoothly variesits displacement volume.

[0093] In alternative embodiments to those of the above preferredembodiments, at least one of the first and second hinge elements 52, 51includes a shaft hole, while the rotor 17 or the swash plate 18 on whichthe hinge element is arranged includes a shaft portion. Also, a pair ofthe first hinge element 52 and the rotor 17 or a pair of the secondhinge element 51 and the swash plate 18 respectively includes shaftholes, and a shaft member is interposed between the shaft holes byinserting the shaft member into the shaft holes.

[0094] In alternative embodiments to those of the above preferredembodiments, the first hinge element 52 or the second hinge element 51has the degree of freedom for slide relative to the rotor 17 or theswash plate 18, respectively.

[0095] In alternative embodiments to those of the above preferredembodiments, at least one of the first and second hinge elements 52, 51has two dimensional degree of freedom for motion against the rotor 17 orthe swash plate 18 on which the hinge element is arranged. For example,one of the first and second hinge elements 52, 51 has the degree offreedom for rotation and for slide relative to the rotor 17 or the swashplate 18, respectively.

[0096] In alternative embodiments to those of the above preferredembodiments, an engaging groove is recessed in a merely disc-shapedrotor (for example, the shape from which the first and second hingeelements 52, 51 are omitted in the above preferred embodiments) or adisc of a swash plate.

[0097] In alternative embodiments to those of the above preferredembodiments, the compressor is a variable displacement compressor thathas a double-headed piston.

[0098] In alternative embodiments to those of the above preferredembodiments, the compressor is a wobble type variable displacementcompressor that has a wobble plate or a cam plate.

[0099] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein but may be modified within thescope of the appended claims.

What is claimed is:
 1. A variable displacement compressor comprising: ahousing defining a cylinder bore; a piston accommodated in the cylinderbore; a drive shaft rotatably supported by the housing; a rotorconnected to the drive shaft so as to rotate integrally with; a camplate supported by the drive shaft so as to incline and slide relativeto the drive shaft, the cam plate being operatively connected to thepiston; and a hinge mechanism interposed between the rotor and the camplate, the hinge mechanism guiding the cam plate to incline and sliderelative to the drive shaft, whereby the displacement volume of thecompressor is varied, the rotation of the drive shaft being converted tothe reciprocation of the piston through the rotor, the hinge mechanismand the cam plate, the hinge mechanism including: a first hinge elementprovided on the rotor; and a second hinge element provided on the camplate, the second hinge element being engaged with the first hingeelement, at least one of the first and second hinge elements having adegree of freedom for motion against the rotor and/or the cam plate towhich the hinge element having the degree of freedom for motion belongs.2. The variable displacement compressor according to claim 1, wherein atleast one of the first and second hinge elements has the degree offreedom for rotation in such a manner that the hinge element ispivotally supported by the rotor and/or the cam plate to which the hingeelement having the degree of freedom for rotation belongs.
 3. Thevariable displacement compressor according to claim 1, wherein at leastone of the rotor and the cam plate that includes the hinge elementhaving the degree of freedom for motion has a regulating means forcontacting to regulate a motion range of the hinge element.
 4. Thevariable displacement compressor according to claim 1, wherein the firsthinge element has a first protrusion arranged on the rotor, the firstprotrusion extending toward the cam plate, the second hinge elementhaving a second protrusion arranged on the cam plate, the secondprotrusion extending toward the rotor and receiving rotational powerfrom the rotor by engagedly contacting the first protrusion, one of thefirst and second hinge elements including a receiving portion forreceiving axial load at its proximal portion of the protrusion, thereceiving portion receiving axial load that acts on the cam plate insuch a manner that the receiving portion slidably contacts a distal endof the protrusion of the other of the first and second hinge elements.5. The variable displacement compressor according to claim 4, whereinthe hinge mechanism further includes a slider that is interposed betweenthe receiving portion and the distal end of the protrusion of the otherof the first and second hinge elements.
 6. The variable displacementcompressor according to claim 4, wherein the hinge mechanism furtherincludes a pin that is connected to one of the first and second hingeelements, the other of the first and second hinge elements including acam groove, the pin being inserted through the cam groove.
 7. Thevariable displacement compressor according to claim 4, wherein at leastone of the first and second protrusions is plurally provided, theplurally provided protrusions being integrated with each other, theintegrated plurally provided protrusions has the degree of freedom formotion against the rotor and/or the cam plate to which the integratedplurally provided protrusions belongs.
 8. The variable displacementcompressor according to claim 7, wherein the number of plurally providedprotrusions is two.
 9. The variable displacement compressor according toclaim 8, wherein the drive shaft is rotated in a predetermineddirection, the two provided protrusions being disposed in thepredetermined direction, one of the provided protrusions on a precedingside in the predetermined direction being formed thicker than the otherof the provided protrusions on a following side in the predetermineddirection.
 10. The variable displacement compressor according to claim7, wherein both the first and second protrusions are plurally provided,each number of the plurally provided protrusions being respectively two.11. The variable displacement compressor according to claim 7, whereinat least one of the first and second hinge elements includes: a basehaving two surfaces; a plurality of the protrusions extending from oneof the surfaces of the base; and a shaft formed on the other of thesurfaces of the base.
 12. The variable displacement compressor accordingto claim 1, wherein the hinge element having the degree of freedom formotion is made of a material that is smaller in relative density thanthe rotor and/or the cam plate to which the hinge element belongs. 13.The variable displacement compressor according to claim 12, wherein thehinge element having the degree of freedom for motion is made ofaluminum series metal, while the rotor and/or the cam plate to which thehinge element belongs is made of iron series metal.
 14. The variabledisplacement compressor according to claim 1, wherein one of the firstand second hinge elements includes a guide protrusion while the other ofthe first and second hinge elements includes a guide groove, the guideprotrusion engaging the guide groove for guiding the cam plate toincline and slide relative to the drive shaft.
 15. The variabledisplacement compressor according to claim 1, wherein the cam plate isformed by forging.
 16. The variable displacement compressor according toclaim 1, wherein at least one of the first and second hinge elements ismade of iron series sintered metal.
 17. The variable displacementcompressor according to claim 1, wherein the compressor is a pistontype.
 18. A hinge element for partially forming a hinge mechanism of avariable displacement compressor, comprising: a base having twosurfaces; a plurality of protrusions extending from one of the surfacesof the base; and a shaft formed on the other of the surfaces of thebase.